Locating abrasive wheels for dressing



Marchl1, 1 958 E. R. DUNN 826:008

LocATING ABRAsIvE WHEELS FOR DREssNGv Filed 'June 29', 1956 2 sheets-shawb 1 INVEN-ron IEVLMAN RJU'NN BY ATTORNEY March 11, 1958 2,826,008

E. R. DUNN l LocATxNG AERAsIvE WHEELS FOR DRESSING All? SUPPLY lNvsN-ron ELMAN n. Jau/wv BY A ATTORNEY .Len

United @rates Patent O LOCATING ABRASWE WHEELS FR DRESSING Elman R. Dunn, Beioit, Wis., assigner to Gardner Machine Company, Beloit,

Application .lune 29, 1956, Serial No. 594,863

7 Claims. (Cl. 51--111) This invention relates to disc grinders particularly double disc grinders and more particularly to means for positioning the abrasive discs in relative longitudinal positions for dressing and for grinding. ln machines of this type, the dressing device consists of a diamond holder having oppositely spaced diamonds for simultaneously engaging each of the abrasive discs. During a grinding operation, the discs are spaced to grind a workpiece to a predetermined thickness, length, or width as the case may be. For semi-automatic dressing, it is necessary that the discs be shifted to a spacing equal to the spacing of the diamonds on the dressing tool. After the dressing operation, the discs must be shifted to the proper spacing for grinding.

An object of this invention is to provide means for shifting the discs a predetermined distance between the grinding and dressing positions.

In present machines of this type, the discs are retracted from grinding position against the resistance or pull of a weight or spring which serves `as a backlash take-up mechanism to maintain a continuous force in one direction on the supporting members of the discs.

Another object of this invention is to provide this one direction force by means of air pressure.

Figure l is a front elevation partly in section and partly cut away to show the means for shifting the heads supporting the abrasive discs between grinding and dressing positions, means for compensating for dressing, and means for controlling the extent of movement of said heads between grinding and dressing positions.

Figure 2 is a hydraulic and electric diagram.

Numeral li) indicates the bed of a disc grinder on which are slidably mounted for longitudinal movement a pair of head members lla and 11b having opposed abrasive discs i3d and 13b pivotally mounted thereon.

Since the head members and the means for actuating them are identical, a description of one is considered sucient. However, suitable reference numerals will be applied to both heads. At the outer end of the head member 1lb is mounted a feed mechanism consisting of a housing Ztlb in which is rotatably mounted a feed screw 2lb having a stop pin 22b mounted in the end toward the bed. Said stop pin 22]; has a spherical stop surface 23b. A gear 24]; mounted on feed screw 2lb engages a pinion 25]; on shaft 2612. A ratchet wheel 27h also attached to shaft Zdb is actuated by pawl 28h which in turn is actuated by means of a piston 32h.

The means for shifting head member 1lb to the right for dressing consists of a cylinder liib mounted in bed 10 and having a piston dlb slidably mounted therein. A piston rod 42h on piston Rib has a spherical stop surface 43b thereon. Spherical surfaces 23b and 43b on stop pin 22h and piston rod 42b respectively are held in a predetermined spaced relation by means of a rod 50h. The length of said rod varies with the thickness of the piece to be ground and determines or is dependent on the distance the member has to move between the grind- 2,826,008 Patented Mar. 11, 1958 ing and dressing positions. The rod is slidably supported in a pair of bushings 51h and 52b in the wall 53h of bed 10. The outer end of bushing 51b serves as a stop for piston rod 42h and stop member 43b. The outer end of bushing 52b serves as a stop for feed screw stop pin 22b. Thus, movement of piston 41h to the right is transmitted through the piston rod 42b through rod 50h, feed screw Zlib and housing 20b to head member 11b.

The means for moving said head member 11b in the opposite direction consist of a cylinder 60h pivotally mounted at 61b in bed 10 Iand having a piston 62b slidably mounted therein and connected to a piston rod 63h. The lower end of arm 70b is pivotally mounted at 7llb. Said piston rod is resiliently connected to arm '791; at an intermediate point. The upper end of arm itlb may be connected by any suitable abutment or linkage to the head member 1lb. The head end of cylinder 6M is connected to a continuous supply of air under pressure and this serves as a cushion to the retracting movement of head member 11b.

Operation Closing the start switch energizes lCR which completes a circuit through lCRl and ln-LS to energize valve solenoid C to direct air under pressure to the upper portion of the booster 6. This pressure acts on a body of hydraulic fluid which is directed from the lower end of said booster to the head ends of cylinders t0n and 40b to separate the abrasive discs 13a and 13b mounted on heads 11a and 11b.

Said start switch also closes a circuit to energize valve solenoids A and B to shift valves 3a and 3b, to direct uid under pressure to the rod end of cylinders 30a and Stlb, to actuate the feed pistons `and pawls 28a and Zb, to advance each of the abrasive discs in accordance with the amount of abrasive to be removed by the dressing tool as it moves to the In position.

Energizing ICR completes a circuit through ICRZ, SLS, and SLS to energize valve solenoid D. SLS and 8LS are positioned to be actuated by the two feed mechanisms. Valve solenoid D initiates the operation of the resser motor Sil to reciprocate the diamond holder 31 across the faces of the abrasive discs 13a and 13b.

As the dresser tool begins its movement to the In position, Out-LS is closed to hold ICR after the start switch is released, and also to keep valve solenoid C energized which in turn keeps the abrasive discs separated.

When the start switch is released, valve solenoids A and B are deenergized so that pawls 28a and Zb are reset. When the dressing tool reaches the In position, it shifts In-LS to complete a circuit around the start switch to again energize valve solenoids A and B to provide another feed increment of the discs in preparation for the movement of the dresser to the Out position.

The In-LS opens the holding circuit to deenergize lCR. 1CR2 opens the circuit to valve solenoid D reversing the movement of the dresser and starting it to the Out position.

When the dresser reaches the Out position, it opens Out-LS to deenergize valve solenoid C which reverses the pressure on the booster 6 so that the pressure on the head ends of cyiinders 40a and 4Gb is released and the constant air pressure in the head ends of cylinders @tia and 60h serves to return the heads 11a and 11b and the discs 13a `and 13a to grinding position in which they are properly located by engagement of stop surfaces 23a and 23h engaging the co-operating surfaces on the bushings 52a and 52h. The dressing tool stops in the Out position unitil it is again actuated by closing the start switch.

In actual practice, the start switch is actuated by a counter or some other conventional control device, The

dressing operation is stopped by a similar control. For y the purpose of illustration, a simple manually actuated start and stop switch is considered sufficient.

i claim:

l. In a disc grinder, a pair of opposed abrasive discs, each having a spindle and a spindle housing for rotatably supporting said discs in axial alignment, slide members for slidably supporting said spindle housing for movement of said discs between grinding and dressing positions, means for performing a dressing operation on said discs comprising a pair of oppositely disposed dressing tools mounted for movement across the annular surfaces of said discs, means for moving said spindle housing to separate said discs, means to stop said separating movement with said discs spaced by an amount equal to or less than the space between the operative surfaces of said dressing tools including removable stop pins for determining the zone of movement of said housing, the length of said pins being inversely proportional to the distance between the surfaces of said abrasive discs when in grinding position, means for adjusting the space between said discs to compensate for wear and dressing, means for retracting said dressing tools from between said discs after the operation of said dressing means, and means operable at the end of a dressing operation to reset said discs in proper spaced relation for grinding workpieces to a predetermined size including an adjustable stop member movable with said spindle housing.

2. In a disc grinder, a pair of opposed abrasive discs, a separate longitudinally movable support for each of said discs, means for performing a dressing operation on the operative surface of said discs comprising a pair of oppositely disposed dressing tools, means for separating said discs by an amount less than the space between the operative surfaces of said dressing tools, means for adjusting the position of said discs to compensate for weer 'and dressing, and means to reset said discs comprising positive stops for locating said discs in a predetermined spaced relation corresponding to the thickness of the workpiece to be ground, an adjustable stop member on said longitudinally movable support members for coacting with said positive stop, and means for actuating said adjustable stop member to compensate for changes in the longitudinal position of said operative surfaces.

3. In a disc grinder, a bed, a spindle housing slidably mounted on said bed, a spindle rotatably mounted therein, an abrasive disc on said spindle, a feed mechanism attached to the end of the slide opposite said disc, said mechanism having a depending portion, an. adjustable stop member in said depending portion, means for moving said housing on said bed in an axial direction cornprising a cylinder, a piston slidably mounted therein, a piston rod on said piston, connections between said piston rod and said adjustable stop including a pin slidably mounted in said bed, a pair of opposed bushings in said bed for slidably supporting said pin, one of said bushings serving as a positive stop for said adjustable stop member, means for moving said spindle housing in the opposite direction including a cylinder, a piston slidably mounted therein, connections between said piston and said spindle housing, means for maintaining continuous pressure in said cylinder in a direction opposite to the retracting movement of said first mentioned piston to provide a cushion for said retracting movement and to return said spindle housing and abrasive disc to grinding position upon the release of pressure in said tirst mentioned cylinder.

4. In a grinding machine, a bed, a grinding wheel support slidably mounted on said bed, a grinding wheel spindle rotatably mounted on said support, an abrasive tool on said spindle, a feed mechanism for moving said tool toward and away from operative position comprising a piston and cylinder, one of which is mounted in said bed, the other of which is connected to said support l`or moving said support away from operative position, a second piston and cylinder connected to said support for moving it toward operative position, a supply of uid under pressure connected to said cylinder to urge said pi^on continuously in a direction opposite to the lirst mentioned piston whereby to provide a cushion for said retracting movement, and to return said support and said abrasive tool to grinding position upon the release of pressure in said iirst mentioned cylinder.

5. ln a disc grinder, a bed, a spindle housing slidably mounted on said bed, a spindle rotatably mounted in said housing, an abrasive disc on said spindle, means for shifting said spindle housing and disc axially on said bed between a grinding position and a dressing position including a cylinder, a piston slidably mounted therein, a piston rod on said piston, means for stopping movemeut of said housing in one direction comprising a stop member on said piston rod, a tiXed stop in the path of said piston rod, an adjustable stop member on said spindle housing, a xed stop in the path of said adjustable member to stop the movement of said housing in the opposite direction, and selective means which vary inversely with the thickness of the workpiece to be ground for maintaining a fixed distance between said movable stop members.

6. In a disc grinder, a bed, a spindle housing slidably mounted on said bed, a spindle rotatably mounted in said housing, an abrasive disc on said spindle, means for shifting said spindle housing and disc axially on said bed between a grinding position and a dressing position including a cylinder, a piston slidably mounted in said cylinder, a piston rod on said piston, connections between said piston rod and said spindle housing including a pin slidably mounted in a pair of oppositely disposed bushings in said bed, an adjustable stop on said housing in the path of said pin, said bushings having stop surfaces for engaging said piston rod and said adjustable stop member respectively in dressing and grinding positions, said pin being of a length determined by the thickness of the workpiece to be ground.

7. In a disc grinder. a pair of opposed abrasive discs, each having a spindle and a spindle housing for rotatably supporting said discs in axial alignment, slide members tor slidably supporting said spindle housing for movement of said discs between grinding and dressing positions, means for performing a dressing operation on said discs comprising a pair of oppositely disposed dressing tools mounted for movement across the annular surfaces of said discs, means for moving said spindle housing to separate said discs, means to stop said separating movement with said discs spaced by an amount equal to or less than the space between the operative surfaces of said dressing tools including removable stop pins for determining the zone of movement of said spindle housmg.

References Cited in the le of this patent UNITED STATES PATENTS 2,254,784 Silven Sept. 2, 1941 2,387,044 Silven Oct. 16, 1945 2,398,463 Rumsey Apr. 16, 1946 FOREIGN PATENTS 689,049 Great Britain Mar, 1S, 1953 

